1. Field of Invention
The present invention relates to a semiconductor process; more particularly, to a method for fabricating a semiconductor device.
2. Description of Related Art
In an ordinary integrated circuit processing, the photolithography and etching technology is commonly used for forming an opening or a trench, for example, in a silicon substrate or a material containing silicon. It is well known in the art that, when the wafer is waiting to be delivered to the next chamber after the opening or the trench to be formed in the silicon substrate or the material containing silicon, the silicon substrate or the material containing silicon at the bottom of the opening or the trench is exposed to an oxygen-containing ambient, for example, oxygen or vapor. Therefore, the silicon atoms in the silicon substrate or the material containing silicon may react with oxygen or vapor in an oxidation reaction to form a silicon dioxide layer , which is also known as a native oxide layer. The formation of the above native oxide layer generates many problems for the subsequent processing. For example, the native oxide layer may increase the resistance at the contact point and reduce the electrical connection performance. Thus, the yield and the reliability of the device are compromised.
Ordinarily, the method for eliminating the native oxide layer is to apply a wet cleaning technique or an in-situ plasma treatment, etc. The above wet cleaning technique utilizes a hydrofluoric acid (HF) solution to eliminate the native oxide layer, and the process is tedious and time-consumable. In addition, the above in-situ plasma treatment may induce damages on the silicon substrate or the material containing silicon at the bottom of the opening or the trench, while the native oxide layer, which eventually leads to a reduction of the yield of and the reliability of the products, is being removed.
For much of the trench devices, a native oxide layer is formed at the bottom of the wafer due to an exposure to the oxygen-containing ambient before filling the trench with a conductive layer. The native oxide layer may generate many problems for the processing, thereby reducing the yield and reliability of the devices.